1. Technical Field
The present invention relates to a driving device and a driving method of a capacitive load formed of a load capacitor, and is particularly suitable for a liquid jet printing apparatus adapted to form a predetermined character or graphics by emitting a jet of a minute liquid to form a fine particle (dot) on a medium.
2. Related Art
An inkjet printer as one of such liquid jet printing apparatuses, which is generally low-price and easily provides high quality color prints, has widely been spreading not only to offices but also to general users along with widespread of personal computers or digital cameras.
A device having a liquid jet head provided with a liquid jet nozzle and mounted on a moving member called a carriage to move in a direction intersecting with a conveying direction of a print medium is generally called “a multi-pass printing apparatus.” In contrast, a device having a liquid jet head elongated in a direction intersecting with the conveying direction of a print medium and capable of performing printing in a single pass is generally called “a line head printing apparatus.”
Incidentally, in the liquid jet printing apparatus of this kind, the drive signal amplified by a power amplifying circuit is applied to a nozzle actuator such as a piezoelectric element to emit a jet of a liquid from a nozzle, and if the drive signal is amplified by an analog power amplifier such as a linearly driven push-pull connected transistor, a substantial power loss is caused, and a large heat sink is required. Therefore, according to JP-A-2005-329710, the drive signal is amplified using a digital power amplifier, thereby reducing the power loss, and eliminating the heat sink.
However, since the actuators such as piezoelectric elements are capacitive loads each having a capacitance, in the case in which the drive signal is amplified using the digital amplifier as disclosed in JP-A-2005-329710, it is required to eliminate the carrier component of the modulated signal to be amplified using an inductor. On this occasion, the inductor and the load capacitor (the capacitive load) are combined to form a filter, moreover the characteristic of the filter varies in accordance with the number of load capacitors connected, and as a result, the drive signal characteristic is varied to vary the liquid jet characteristic. Further, in order for suppressing the resonance of the filter, a damping resistor is usually inserted between the inductor and the load capacitor, and the damping resistor causes a further power loss.